Solar Viewing Projector
There are many ways to view a solar eclipse. The safest (and most fun!) is to make your own solar viewing projector. This technique of using a small hole to focus light goes back to the 5th century BC. In the 4th century, BC, Aristotle wrote:
"Why is it that when the sun passes through quadri-laterals, as for instance in wickerwork, it does not produce a figure rectangular in shape but circular?” and further "Why is it that an eclipse of the sun, if one looks at it through a sieve or through leaves, such as a plane-tree or other broadleaved tree, or if one joins the fingers of one hand over the fingers of the other, the rays are crescent-shaped where they reach the earth? Is it for the same reason as that when light shines through a rectangular peep-hole, it appears circular in the form of a cone?”
And Leonardo da Vinci wrote of this property in the 16th century noting:
"When the images of illuminated objects pass through a small round hole into a very dark room…you will see on paper all those objects in their natural shapes and colours." "Who would believe that so small a space could contain the image of all the universe? O mighty process! What talent can avail to penetrate a nature such as these? What tonque will it be that can unfold so great a wonder? Verily, none! This it is that guides the human discource to the considering of divine things. Here the figures, here the colors, here all the images of every part of the universe are contracted to a point. O what a point is so marvelous!."
Later, this method of focusing light would be used in the "Camera Obscura" to take the first photographs.
You can recreate a piece of history and have fun observing the sun!